The present invention is a continuation-in-part of co-pending application Ser. No. 07/426,959 filed Oct. 24, 1989 which is a continuation-in-part of co-pending application Ser. No. 07/423,902 filed Oct. 19, 1989 which is a continuation-in-part of co-pending application Ser. No. 193,964 filed May 13, 1988, now U.S. Pat. No. 5,079,334; and, which the entire disclosure of each application is expressly incorporated herein by reference.
The present invention relates to sulfonic acid-substituted polyaniline salt compositions, their derivatives and uses thereof.
Polyaniline is a family of polymers that has been under intensive study recently because the electronic, chemical and optical properties of the polymers can be modified through variations of either the number of protons, the number of electrons, or both. The polyaniline polymer can occur in several general forms including the so-called reduced form (leucoemeraldine base), possessing the general formula ##STR1## the partially oxidized so-called emeraldine base form, of the general formula ##STR2## and the fully oxidized so-called pernigraniline form, of the general formula ##STR3##
In practice, polyaniline generally exists as a mixture of the several forms with a general formula (I) of ##STR4##
When 0.ltoreq.y.ltoreq.1, the polyaniline polymers are referred to as poly(paraphenyleneamineimines) in which the oxidation state of the polymer continuously increases with decreasing value of y. The fully reduced poly(paraphenyleneamine) is referred to as leucoemeraldine, having the repeating units indicated above corresponding to a value of y=1. The fully oxidized poly(paraphenyleneimine) is referred to as pernigraniline, of repeat unit shown above corresponds to a value of y=0. The partly oxidized poly(paraphenyleneamineimine) with y in the range of greater than or equal to 0.35 and less than or equal to 0.65 is termed emeraldine, though the name emeraldine is often focused on y equal to or approximately 0.5 composition. Thus, the terms "leucoemeraldine", "emeraldine" and "pernigraniline" refer to different oxidation states of polyaniline. Each oxidation state can exist in the form of its base or in its protonated form (salt) by treatment of the base with an acid.
The use of the terms "protonated" and "partially protonated" herein includes, but is not limited to, the addition of hydrogen ions to the polymer by, for example, a protonic acid, such as mineral and/or organic acids. The use of the terms "protonated" and "partially protonated" herein also includes pseudoprotonation, wherein there is introduced into the polymer a cation such as, but not limited to, a metal ion, M.sup.+. For example, "50%" protonation of emeraldine leads formally to a composition of the formula ##STR5## which may be rewritten as ##STR6##
Formally, the degree of protonation may vary from a ratio of [H.sup.+ ]/[--N.dbd.]=0 to a ratio of [H.sup.+ ]/[--N.dbd.]=1. Protonation or partial protonation at the amine (--NH--) sites may also occur.
The electrical and optical properties of the polyaniline polymers vary with the different oxidation states and the different forms. For example, the leucoemeraldine base, emeraldine base and pernigraniline base forms of the polymer are electrically insulating while the emeraldine salt (protonated) form of the polymer is conductive. Protonation of emeraldine base by aqueous HCl (1M HCl) to produce the corresponding salt brings about an increase in electrical conductivity of approximately 10.sup.12 ; deprotonation occurs reversibly in aqueous base or upon exposure to vapor of, for example, ammonia. The emeraldine salt form can also be achieved by electrochemical oxidation of the leucoemeraldine base polymer or electrochemical reduction of the pernigraniline base polymer in the presence of an electrolyte of the appropriate pH. The rate of the electrochemical reversibility is very rapid; solid polyaniline can be switched between conducting, protonated and nonconducting states at a rate of approximately 10.sup.5 Hz for electrolytes in solution and even faster with solid electrolytes. (E. Paul, et al., J. Phys. Chem. 1985, 89, 1441-1447). The rate of electrochemical reversibility is also controlled by the thickness of the film, thin films exhibiting a faster rate than thick films. Polyaniline can then be switched from insulating to conducting form as a function of protonation level (controlled by ion insertion) and oxidation state (controlled by electrochemical potential). Thus, polyaniline can be turned "on" by either a negative or a positive shift of the electrochemical potential, because polyaniline films are essentially insulating at sufficiently negative (approximately 0.00 V vs. SCE) or positive (+0.7 V vs. SCE) electrochemical potentials. Polyaniline can also then be turned "off" by an opposite shift of the electrochemical potential.
The conductivity of polyaniline is known to span 12 orders of magnitude and to be sensitive to pH and other chemical parameters. It is well-known that the resistance of films of both the emeraldine base and 50% protonated emeraldine hydrochloride polymer decrease by a factor of approximately 3 to 4 when exposed to water vapor. The resistance increases only very slowly on removing the water vapor under dynamic vacuum. The polyaniline polymer exhibits conductivities of approximately 1 to 20 Siemens per centimeter (S/cm) when approximately half of its nitrogen atoms are protonated. Electrically conductive polyaniline salts, such as fully protonated emeraldine salt [(--C.sub.6 H.sub.4 --NH--C.sub.6 H.sub.4 --NH.sup.+)--Cl.sup.- ].sub.x, have high conductivity (10.sup.-4 to 10.sup.+2 S/cm) and high dielectric constants (20 to 200) and have a dielectric loss tangent of from below 10.sup.-3 to approximately 10.sup.1. Dielectric loss values are obtained in the prior art by, for example, carbon filled polymers, but these losses are not as large nor as readily controlled as those observed for polyaniline.
Electrochemistry of molecular materials can be affected without using liquid electrolyte solutions as discussed in Skotheim, T. A., et al. J. Electrochem. Soc., 1985, 132, 2116. It is also well appreciated that solid-state ionic conductors are useful in battery and fuel-cell applications. Obayashi, H., et al. Adv. Chem. Ser., 1977, 163, 316. Solid-state photoelectrochemical devices that involve the use of solid-state ionic conductors have been reported in Sammels, A. F., et al., J. Electrochem. Soc., 1984, 131, 617. A solid-state PAN-based transitor is also reported in Chao, S., et al., J. Am. Chem. Soc., 1987, 109, 6627.
The first generation of polymer solid electrolyte was based on alkali metal salts dissolved in polyethers such as high molecular weight (M.W. 600,000) poly(ethylene oxide) (PEO), (--CH.sub.2 CH.sub.2 O--).sub.n. The absense of solvents and reactive groups results in a wide electrochemical stability window and therefore compatibility with highly reactive electrode materials. In addition, single ionic conductivity has been achieved in sodium poly(styrene sulfonate) as discussed in Hurdy, L. C., et al., J. Am. Chem. Soc., 1985, 107, 3823.
The preparation of sulfonated polyaniline compositions, which are capable of being "self-protonated" or "self-doped", are disclosed in the co-pending application Ser. No. 07/423,902, filed on Oct. 19, 1989, the entire disclosure of which is expressly incorporated herein by reference.
The present invention also relates to the co-pending parent application Ser. No. 07/426,959 filed Oct. 24, 1989, which disclosed the preparation of sulfonated polyaniline salt compositions, the entire disclosure of which is expressly incorporated herein by reference.